Anatomy & Physiology - Cell Structure
Anatomy & Physiology - Cell Structure 80197 - BIOL 2220 - 001
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80197 - BIOL 2220 - 001
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This 7 page Class Notes was uploaded by Courtney Luber on Tuesday September 6, 2016. The Class Notes belongs to 80197 - BIOL 2220 - 001 at Clemson University taught by John R Cummings in Fall 2016. Since its upload, it has received 4 views. For similar materials see Human Anatomy and Physiology I in Biology at Clemson University.
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Date Created: 09/06/16
Cell Structure Cell o Latin – cella – chamber/storehouse o Definition – the basic living, structural and functional units of all organisms o If not made of cells, not living o 200 different types of cells in human body o 1 x 10 cells in the human body o Smallest cell is 2 microns (1 millionth of a meter) o Largest cell is more than a meter in size (neuron) Cell Theory o Cell is structural and functional unity of life o Activity of organism is combined results of individual and aggregated cells o Activity of cells depends on subcellular composition Structure and function Principle of complementarity – the action of the cell is determined by the things the cell possesses o Cells are responsible for the continuity of life Parts of a cell o Plasma membrane – separates inside from outside; limiting boundary inside can have a different composition o Organelles – no cell possesses all organelles Each carries out a specific function o Cytoplasm – fluid on inside of cell; intracellular fluid Organelles suspended in this fluid In order to be biologically active, all chemicals have to be in solution – cytoplasm keeps cells functional Composition of Plasma Membrane o Phospholipid bilayer Glycerol attached to phosphate and two fatty acids; polar heads (hydrophilic) and nonpolar tails (hydrophobic) Half of the mass of the mass of the plasma membrane is the phospholipids, while the other half is from proteins o Integral proteins Protein that goes through both parts of the bilayer Mostly transport proteins – allow polar things to move into and out of the cell o Peripheral proteins Protein that is only on one side of the bilayer; usually on inside Mechanically natured – usually act as enzymes o Some proteins have a carbohydrate extension – glycoprotein Carb part is basically a receptor o Carbohydrate chain can also attach to lipid – glycolipid Still a receptor o Width of plasma membrane is 7-10 nm in size (7-10 billionths of a meter) Very thin and fragile; proteins help hold it together Functions of Plasma Membrane o Separate cells from the external environment o Insides can have a different chemical environment than outside o Facilitate contact with other cells or foreign substances o Provide receptor sites o Controls flow into and out of cell Selectively permeable – allows some things to pass and prevents other things from passing o Determines what the internal environment is going to be like because of selectively permeable membrane Determining Factors o Molecular size of the molecule if too big, it generally can’t get in o Solubility fat soluble substances can pass directly across the lipid part of the plasma membrane; water soluble things can’t o Ionic charge something that has the same charge gets pushed away from the cell, while things with opposite charges get pulled near o Carrier molecules Integral proteins that allow thing to pass Membrane Transport Processes o Passive No assistance from the cell; no energy needed Follow a concentration gradient (high concentration low concentration) Small things move faster than big things o Active Cell has to assist movement; provides ATP as energy for the process Moves against the concentration gradient (low high) Passive Processes o Simple diffusion – the passive movement of a substance (liquid, solid, gas) from an area of high concentration to an area of low concentration until we reach equilibrium; then continued movement, but no net change Nonpolar substances and lipids Affected by molecular size, temperature o Facilitated diffusion – involves either a carrier or channel protein No energy required, but protein is Glucose, ions Carrier proteins are specific to certain things; channel proteins are not – just has to fit o Osmosis – movement of water across a selectively permeable membrane Is regulated by solute concentration and osmotic pressure Tonicity Isotonic o If the concentrations are equal o Net movement of water is 0 Hypertonic o The more concentrated solution Hypotonic o The less concentrated solution o Water always moves from hypo- to hyper- o Tries to make the two solutions equal Osmolarity o The tonicity (concentration; # of particles) * the number of particles we get when the substance dissociates o 1 molar saline solution is a 2 osmol solution o It’s the number of particles, not type of particle, that determines the movement of water o Filtration – movement across the membrane that is caused by pressure or gravity Follows pressure gradient Blood is filtered; higher blood pressure filtered more Active processes o Active transport – requires a carrier protein (specific to certain molecules) Energy is required to change the shape of the protein 40% of energy produced by a cell is used by active transport Low high concentration o Exocytosis – cell has to create a vesicle Vesicular transport – transport requiring a vesicle Our cells produce something, a vesicle surrounds it, vesicle is phospholipid bilayer, and now since the bilayer is made of lipids, it meshes with the cells and is able to move out o Endocytosis – same process but used to move something inside the cell Phagocytosis – engulfing of large solid molecules i.e. macrophage consuming blood clots Pinocytosis – engulfing liquid that contains some solid molecule(s) “cell drinking” Receptor-mediated endocytosis – when cell brings in something specific via receptors i.e. want to bring in insulin, iron, or enzyme there is a specific receptor for it clathrin – protein coating on cytoplasmic face of vesicle o “clathrin-coated vesicles” This is how flu gets into our cells it binds to clathrin Plasma Membranes Specializations o Microvilli – tiny projections on the free surface of the cell; increase surface area of cell i.e. surface of intestines or kidneys o Tight junctions – when integral proteins bind to one another, it creates this “impermeable junctions” nothing can pass across these junctions o Desmosomes – when filaments on cell intertwine and hold each other together “anchoring junctions” See these in sheets of tissue where the cells are being exposed to tension such as friction i.e. in heart, skin o Gap junctions - facilitate exchange between adjacent cells “communicating junctions” Can move from one cell directly into another cell; allow faster exchanges Connexon – where the gap junction occurs Allows cells to work as a group instead of as individuals Membrane potentials o Differences in electrical charges across a membrane o Results from distribution of ions on both sides of membrane’ Predominantly potassium, sodium, and chloride o Can result in a voltage difference Resting membrane potential o Sodium potassium pump- pumps potassium ions inside and sodium ions outside More potassium inside than outside; more sodium outside than inside More positive outside the cell than inside the cell – cell is negative; charge is negative o Cell is polarized, with inside negative compared to outside Unequal movement of ions creates a polarity on each side of the cell which is regulated by plasma membrane Parts of a Cell o Plasma membrane o Organelle Organelle o Latin – organelle – tool; instrument o Specialized portion of cell that has a particular shape and does a particular task o Types: Nucleus – largest intracellular structure; most cells only have 1; some don’t have any; some have more than 1 ; brain of the cell Components: o Genetic material – material that controls structure and activity of cell o Nuclear envelope – phospholipid bilayer o Pores – holes in the membrane; things pass into and out of the nucleus o Nucleoplasm – solution inside of the nucleus o Nucleoli – spherical body inside nucleus; some have more than 1; assemble ribosomes which will then pass out of the pores into the cytoplasm (ribosomes - where proteins are made); does not have a membrane Mitochondria – powerhouse of the cell; ATP producer; phospholipid bilayer Can self-replicate Possess their own DNA – mitochondrial DNA comes from only mom Mitochondrial DNA can be used for relatability studies Ribosomes Nucleolus assembles ribosomes Made of RNA and protein subunits “Factory” Site of protein synthesis Tiny granules that can be found directly in cytoplasm or associated with other organelles “attached ribosomes” – attached to something o Make proteins used outside the cell o “export proteins” o Makes plasma membrane proteins o Attached to endoplasmic reticulum “free ribosomes” – not attached to anything; freely swimming in cytoplasm o Make proteins used within the cell Endoplasmic Reticulum Rough ER - attached proteins attached to ER o Makes proteins that are secreted from the cell o Makes integral proteins that become part of plasma membrane o Makes phospholipids of plasma membrane o Close to nucleus Smooth ER – involved with lipid metabolism o Involved in production of steroid hormones o Associated with detoxification for the cell o Involved with the breakdown of glycogen Golgi apparatus – “post office” Proteins produced by rough ER make their way to the Golgi apparatus which modifies them slightly and packages them up for export Puts it into a vesicle exocytosis Lysosomes – Secretes enzyme contents and breaks the cell apart when cell gets old Primary function is to contain enzymes which break down things that come into the cell during phagocytosis Peroxisomes Have enzymes that break down free radicals Free radicals – hydrogen ions o Accumulation is toxic to cell Free radicals converted to hydrogen peroxide (also toxic), so then it is broken down into water Enzymes that detoxify Enzymes produced in free ribosomes Cytoplasm o Elements Cytosol Liquid part inside cell Cytoskeleton Microtubules – hollow protein tubules; distributes organelles within cytoplasm; gives some structure o Important when cell is getting ready to divide Microfilaments – smaller; *the longer the word, the smaller the size* ; very thin strands; run near the surface of the cell/right inside plasma membrane o Change shape of the cell Intermediate filaments – intermediate size; tough insoluble fibers that impart strength to the cell Inclusions – things stored within cell i.e. lipid stored within cell i.e. glycogen; melanin; mucus Cilia - extensions on plasma membrane Extend on apical layer Numerous tiny projections i.e. on respiratory tract; in parts of the female reproductive tract Flagella – single long extension only human cell that possesses a flagella is sperm Centrosome – point of attachment for microtubules; anchor point Centrioles – modifications that appear during cell division and are part of mitotic spindle; migrate to opposite poles; attach to chromosomes and pull them to opposite poles
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